1·More recently, so-called “heliographs” have been used to relay military signals in a similar way.
更近一点例子是，“日光反射信号器”一直通过类似的方式传递军事信号。
2·More recently, so-called "heliographs" have been used to relay military signals in a similar way.
更近一点例子是，“日光反射信号器”一直通过类似的方式传递军事信号。